(1) Field of the Invention
This invention relates to multi-spindle boring apparatus wherein the spindles may be moved simultaneously in a predetermined pattern.
(2) Discussion of the Prior Art
For many years multiple spindle drilling heads have been employed in large industrial drilling machines to simultaneously drill a group of spaced holes in a workpiece. These simultaneous drilling operations provide significant time savings over single drill units which require that either the drill or the workpiece be traversed and a new drilling operation set up for each hole. While multiple drill heads with spindles in a fixed position can operate rapidly to form corresponding holes in a workpiece, it is necessary to change the drill head or to employ another machine to drill holes in a different position. Consequently, some attempts have been made to develop multiple spindle drill heads which facilitate the adjustment of the drill spindles to a plurality of positions.
One known adjustable multiple spindle drilling unit employs at least two spaced, circular frames provided with a guide structure having radially extending slots which receive and provide a guideway for drill supporting heads that extend between the frames. To move these heads along the guideways in the frames, screw shafts are connected to each head and extend radially outwardly therefrom in substantial alignment with the longitudinal axis of each slot. A pinion gear is affixed to an outer portion of each screw shaft and is meshed with a circular gear wheel which also meshes with the remaining pinions. Thus, when any screw shaft is rotated to vary the position of a drill supporting head, the position of the remaining heads is equally varied. This structure is particularly well illustrated by U.S. Pat. No. 706,811 to George H. Everson.
Although constructions similar to that disclosed by the Everson patent to permit a plurality of drill spindles to be simultaneously moved from first corresponding positions to second corresponding positions over equal distances, these structures present a number of practical problems. For example, the lead screws extend outwardly along the longitudinal axes of the guide slots like the spokes of a wheel. As the drill spindles and their associated supporting heads are moved outwardly, the operating lead screws also move outwardly and require additional space. Thus the length of the guide slots is limited by the space available to accomodate the lead screw shafts and the degree of movement available for the drill spindles is likewise limited. In cases where it is desirable to use side by side drill heads with multiple spindles to accomplish both drilling and tapping simultaneously, the structure of the Everson patent is completely unsuitable, as the projecting lead screws from one drill head will contact the upright structure of the adjacent drill head.
Additionally, the sandwiching of spindle carrying heads between slotted sections of two spaced frames results in a lack of drill spindle rigidity which requires the use of drill jigs if accurate workpiece drilling is to be accomplished. Large industrial drills may be subjected to drilling pressures in excess of 20,000 psi, and consequently any movement of the Everson spindle support heads between the spaced circular frames will result in drilling inaccuracies.
Another known apparatus for simultaneously adjusting a plurality of drill spindles over equal distances employs a plurality of rotatable cylindrical members having peripherally disposed gear teeth. A centrally disposed rotatable control member carries gear teeth which mesh with the gear teeth of the cylindrical members so that rotation of the control member rotates all of the cylindrical members. Each cylindrical member carries an eccentrically positioned drill spindle, so that as the cylindrical members are rotated, the drill spindles change position. This construction is illustrated by U.S. Pat. No. 3,203,282 to Charles R. Wilson.
From a consideration of the Wilson patent, it becomes obvious that the degree of movement provided for each drill spindle is extremely limited, for the diameter of the supporting cylindrical members cannot be too large. With this structure, if a large number of drill spindles was required, the movement available for each spindle would be minute.
Although the simultaneous movement of a plurality of drill spindles over equal distances is highly desirable, the limitations of known structures for accomplishing this purpose have generally led to the development of multiple spindle drill heads wherein each spindle is individually adjustable such as illustrated in the U.S. Pat. No. 3,765,786 to Oeckl. This individual adjustment of each drill spindle to initially set up a drilling machine for simultaneous multiple drilling is both time consuming and subject to error. Additionally, such devices are not subject to automation and require a great deal of operator attention.